In a typical gas turbine engine used in a powerplant application, a plurality of combustors is arranged in an annular array about a centerline of the engine. The combustors receive pressurized air from the engine's compressor, add fuel to create a fuel/air mixture, and ignite the mixture to produce hot combustion gases. The hot combustion gases exit the combustors and enter a turbine, where the expanding gases are utilized to drive a turbine, which is in turn coupled through a shaft to the compressor. The engine shaft is also coupled to a shaft that drives a generator for generating electricity.
The combustors typically include at least a pressurized case and a combustion liner contained within the case. The fuel, which is supplied by a plurality of fuel nozzles, mixes with air and reacts (i.e. ignites) within the combustion liner. However, in order for the fuel/air mixture to combust, the mixture must be exposed to a flame source, which is initially generated by an igniter, such as a spark igniter. An igniter, or other peripheral device, such as a flame detector, has access to the contents of the combustion liner through one or more holes placed within a sidewall of the combustion liner. Through these holes, the igniter can extend or the flame detector can detect evidence of a flame in the combustor.
Prior art configurations of combustion liners having openings for igniters and flame detectors have included a washer-like component that can slide laterally and rotate. An example of a prior art opening in a combustion liner is shown in FIGS. 1 and 2. The prior art configuration included a boss 100 extending radially outward from the combustion liner, a floating collar 102 and a cap 104 that is secured to the boss 100 in such a way to retain the floating collar 102, but permit the floating collar 102 to slide and rotate. As compressed air passes along the outside of the combustion liner, the airstream causes the floating collar to vibrate and rotate, often contacting the peripheral device. This movement causes the floating collar 102, which is often time made from a nickel-based alloy such as Hastelloy X, to wear on the igniter or flame detector components, which are typically made of a softer material such as stainless steel. Furthermore, such contact also causes excessive wear and fracturing of the floating collars 102, requiring premature replacement of the peripheral devices.